Microwave-assisted preparation of carboxylic graphene oxide-chitosan composite for adsorption of uranium and heavy toxic metals in water samples

In this study, the microwave-assisted novel composite of carboxylic graphene oxide-chitosan (COOH-GO-CTS) was prepared by using carboxylic functionalized graphene oxide (COOH-GO). The prepared composite was characterized by FTIR, SEM, XRD, XPS and Raman spectroscopy successfully. The composite was used as an adsorbent material for the removal of heavy metals such as uranium (U), lead (Pb), chromium (Cr), and cadmium (Cd). Batch adsorption was carried out to study the effects of pH of the medium, initial concentration of heavy metals, amount of adsorbent dosage, contact time, and temperature. The removal percentages for U, Pb, Cr, and Cd were observed to be 92.4, 94.6, 90.2, and 90.6% at 5, 5.5, 3, and 5 pH, respectively. Adsorption isotherms were performed for Langmuir and Freundlich adsorption, and it was observed that the Langmuir adsorption isotherm well fitted (R-2 > 0.99) the present adsorption study. The maximum adsorption capacities of the composite for U, Pb, Cr, and Cd were found to be 64.93, 384.61, 68.49, and 49.50 mg g(-1), respectively. The heavy metal adsorption kinetics were also performed, and it was observed that the pseudo-second order was well fitted (R-2 > 0.99) the present study. Further, the themodynamic studies confirmed the adsorption of the heavy metals to be endothermic and spontaneous in nature.